Photo sensor, display panel having the same and display device having the display panel

ABSTRACT

A photo sensor includes a first substrate, a switching element and a second substrate. The switching element is disposed at the first substrate and defined by a control electrode, and first and second current electrodes. The switching element includes a channel disposed between the first and second current electrodes. The channel has a first length to receive an incident external light. The second substrate includes a light receiving unit that is disposed corresponding to the channel. The light receiving unit has a second length longer than the first length and shorter than a third length of the control electrode.

This application claims priority to Korean Patent Application No.2004-104219, filed on Dec. 10, 2004, and all the benefits accruingtherefrom under 35 U.S.C § 119, and the contents of which in itsentirety are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photo sensor, a display panel havingthe same and the display device having the display panel.

2. Description of the Related Art

Generally, a liquid crystal display device is classified as either atransmissive type liquid crystal display device, which displays imagesusing an internal light source such as a backlight assembly, or atransmissive and reflective type liquid crystal display device whichdisplays images using the internal light source or by reflecting anexternal incident light.

The transmissive and reflective type display device controls powersupplied to a backlight assembly in response to an intensity of theexternal incident light. Specifically, when the external incident lighthas a lower intensity, the transmissive and reflective type displaydevice operates in a transmission mode such that the backlight assemblyis turned on and internal light transmitted by the backlight assembly isused to display images. When the external incident light has a higherintensity, the transmissive and reflective type display device operatesin a reflective mode such that the backlight assembly is turned off andthe external incident light is reflected to display images.Additionally, a gamma level is automatically adjusted corresponding toeither the transmission mode or the reflective mode so that an imagedisplaying quality is improved.

Thus, power consumption of the transmissive and reflective type displaydevice is reduced by controlling a power supplied to the backlightassembly in response to the intensity of the external incident light.Additionally, when the gamma level is adjusted according to a respectiveoperational mode of the liquid crystal display device, the imagedisplaying quality is improved. Accordingly, a photo sensor disposed ona display panel of the liquid crystal display device to sense theintensity of the external incident light is required to reduce the powerconsumption of the liquid crystal display device.

SUMMARY OF THE INVENTION

Accordingly, the present invention is provided to substantially obviateone or more problems due to limitations and disadvantages of the relatedart. Exemplary embodiments of the present invention provide a photosensor having improved reliability.

In an exemplary embodiment of the present invention, a photo sensorincludes a first substrate, a switching element and a second substrate.The switching element is disposed at the first substrate and defined bya control electrode, and first and second current electrodes. Theswitching element includes a channel disposed between the first andsecond current electrodes. The channel has a first length to receive anincident external light. A light receiving unit is disposed at thesecond substrate corresponding to the channel. The light receiving unithas a second length longer than the first length and shorter than athird length of the control electrode.

The second length of the light receiving unit includes a margin toaccount for misalignment between the first and second substrates.Particularly, the second length of the light receiving unit extendsbeyond both ends of the channel in a direction substantiallyperpendicular to a longitudinal direction of the first and secondcurrent electrodes by a first margin.

Exemplary embodiments of the present invention also provide a displaypanel having the above photo sensor. In some exemplary embodiments ofthe present invention, the display panel includes an array substrate, aliquid crystal layer and an opposing substrate. The array substrate hasan active area on which a first switching element is disposed and asensing area on which a second switching elements is disposed. Thesecond switching element has a channel of a first length. The opposingsubstrate is combined with the array substrate to receive the liquidcrystal layer and includes sensor windows corresponding to the sensingarea. The sensor window has a second length longer than the first lengthand shorter than a third length of a control electrode of the secondswitching element.

Exemplary embodiments of the present invention also provide a displaydevice having the above display panel. In some exemplary embodiments ofthe present invention, the display device includes a display unit, alight sensing unit, a driving controller and a light generation unit.The display unit has pixel electrodes disposed at a first substrate anda color filter disposed at a second substrate corresponding to the pixelelectrodes to display images. The light sensing unit includes aswitching element having a channel of a first length disposed at thefirst substrate and a sensor window having a second length disposed atthe second substrate to sense an amount of an external light. The secondlength is longer than the first length. The driving controller outputs adriving control signal responsive to the amount of external light sensedby the light sensing unit. The light generation unit provides thedisplay unit with an internal light controlled by the driving controlsignal.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more apparent to those of ordinaryskill in the art by describing, in detail, exemplary embodiments thereofwith reference to the attached drawings, wherein like elements arerepresented by like reference numerals, which are given by way ofillustration only and thus do not limit the exemplary embodiments of thepresent invention.

FIG. 1 is a plan view illustrating a photo sensor according to anexemplary embodiment of the present invention.

FIG. 2 is a cross sectional view taken along line I-I′ in FIG. 1.

FIG. 3 is a plan view illustrating a photo sensor according to anexemplary embodiment of the present invention.

FIG. 4 is a plan view illustrating a photo sensor according to anexemplary embodiment of the present invention.

FIG. 5 is a plan view illustrating a photo sensor according to anexemplary embodiment of the present invention.

FIG. 6 is a plan view illustrating a photo sensor according to anotherexemplary embodiment of the present invention.

FIG. 7 is a plan view illustrating a photo sensor according to anotherexemplary embodiment of the present invention.

FIG. 8 is a plan view illustrating a photo sensor according to anotherexemplary embodiment of the present invention.

FIG. 9 is a plan view illustrating a photo sensor according to anotherexemplary embodiment of the present invention.

FIG. 10 is a plan view illustrating a photo sensor according to stillanother exemplary embodiment of the present invention.

FIG. 11 is a plan view illustrating a photo sensor according to stillanother exemplary embodiment of the present invention.

FIG. 12 is a plan view illustrating a photo sensor according to stillanother exemplary embodiment of the present invention.

FIG. 13 is a plan view illustrating a photo sensor according to stillanother exemplary embodiment of the present invention.

FIG. 14 is a partial plan view illustrating a display panel according toan exemplary embodiment of the present invention.

FIG. 15 is a cross sectional view taken along line II-II′ in FIG. 14.

FIG. 16 is a schematic plan view illustrating a display device accordingto another exemplary embodiment of the present invention.

FIG. 17 is a circuit diagram illustrating an operation of a photo sensorin FIG. 16.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be explained in detail withreference to the accompanying drawings.

FIG. 1 is a plan view illustrating a photo sensor according to anexemplary embodiment of the present invention. FIG. 2 is a crosssectional view taken along line I-I′ in FIG. 1.

Referring to FIGS. 1 and 2, the photo sensor includes a first substrate100, a second substrate 200 facing the first substrate 100 and aninsulating layer 300 disposed between the first and second substrates100 and 200.

The first substrate 100 includes a photo switching element (e.g.,amorphous silicon thin film transistor (a-Si TFT)) 110 formed on a firstbase substrate 101. The photo switching element 110 includes anamorphous silicon layer for forming a channel.

The photo switching element 110 has a gate electrode 111 formed from afirst metal layer, and source electrode 113 and a drain electrode 114formed from a second metal layer. A semiconductor layer 112 is disposedbetween the gate electrode 111 and the source and drain electrodes 113and 114. The semiconductor layer 112 includes an activation layer 112 aand a resistive contact layer (a-Si:H) 112 b.

A portion of the resistive contact layer 112 b is removed correspondingto the source and drain electrodes 113 and 114 to form a channel (CH) inthe semiconductor layer 112, and the activation layer 112 a is exposedthrough the channel (CH). The channel (CH) has a first length L1 and afirst width W1. A resistance of the channel (CH) is varied in responseto an amount of an external light incident on the channel (CH) andaccordingly, an amount of current flowing through the channel (CH) isvaried in response to the amount of the external light incident on thechannel (CH).

A gate insulation layer 102 is disposed over the gate electrode 111 anda passivation layer 103 is disposed over the source and drain electrodes113 and 114 and exposed portions of the gate insulation layer 102.

The second substrate 200 includes a second base substrate 201 and alight blocking layer 210 disposed at the second base substrate 201. Asensor window 211 is disposed at the light blocking layer 210corresponding to the channel (CH) of the photo switching element 110.The sensor window 211 has a second length L2 and a second width W2.

A relationship exists between sizes of the photo switching element 110and the sensor window 211. The second length L2 of the sensor window 211is longer than the first length L1 of the channel (CH). The second widthW2 of the sensor window 211 is wider than the first width W1 of thechannel (CH).

Particularly, the sensor window 211 is extended with respect to thefirst length L1 in a direction substantially perpendicular to alongitudinal direction of the source and drain electrodes 113 and 114 bya first margin ΔL1, to account for a misalignment between the first andsecond substrates 100 and 200. In other words, the second length L2 ofthe sensor window 211 is longer than the first length L1 of the channel(CH) by twice the first margin ΔL1.

Thus, the sensor window 211 is extended to the second length L2 toassure receipt of the external light incident on the channel (CH) evenwhen the misalignment occurs in the photo sensor. It is desirable thatthe first margin ΔL1 is about 7 μm when the first length L1 is about 4μm. In other words, the second length L2 of the sensor window 211 is atleast about 18 μm.

The gate electrode 111 of the photo switching element 110 has a largerarea than the sensor window 211 to prevent light exiting a lower portionof the first base substrate 101 from leaking out through the sensorwindow 211. For example, the gate electrode 111 may be extended fromboth marginal edges of the sensor window 211 by a second margin ΔL2,respectively, to have a third length L3. A width of the gate electrode111 is about W2 plus two times the second margin ΔL2. It is desirablethat the third length L3 of the gate electrode 111 is at least about 38μm when the second length L2 of the sensor window 211 is at least about18 μm. In other words, for example, when the first margin ΔL1 is about 7μm, the second margin ΔL2 is about 10 μm.

FIG. 3 is a plan view illustrating a photo sensor according to anexemplary embodiment of the present invention.

Referring to FIG. 3, a photo switching element 120 is disposed at afirst substrate 100. The photo switching element 120 includes a gateelectrode 121 formed from a first metal layer, and a source electrode123 and a drain electrode 124 formed from a second metal layer. Asemiconductor layer 122 is disposed between the gate electrode 121 andthe source and drain electrodes 123 and 124.

A portion of a resistive contact layer is removed corresponding to thesource and drain electrodes 123 and 124 to form a channel on thesemiconductor layer 122, wherein an activation layer is exposed throughthe channel.

As shown in FIG. 3, the source and drain electrodes 123 and 124 are eachformed in a shape of teeth of a comb. The channel defined by the sourceand drain electrodes 123 and 124 has a length L1 and is disposed in azigzag pattern having a width W1. Accordingly, a ratio of the width W1of the zigzag pattern to the length L1 of the channel is increased toimprove characteristics of the photo switching element 120. A resistanceof the channel is varied in response to an amount of external lightincident on the channel and accordingly, an amount of current flowingthrough the channel is varied to detect the amount of the external lightincident on the channel.

The sensor window 211 corresponding to the photo switching element 120is defined on the second substrate 200 by the light blocking layer 210.The sensor window 211 has a second length L2 and a second width W2.

The photo switching element 120 has the following relationship withrespect to the sensor window 211. The second length L2 of the sensorwindow 211 corresponds to the first width W1 of the channel of the photoswitching element 120. In addition, the second length L2 of the sensorwindow 211 includes a first margin ΔL1 to account for misalignmentbetween the first and second substrates 100 and 200.

Particularly, the second length L2 of the sensor window 211 is extendedin a direction perpendicular to a longitudinal direction of the sourceand drain electrodes 123 and 124 by the first margin ΔL1 to account forthe misalignment between the first and second substrates 100 and 200.

Thus, the sensor window 211 is extended to the second length L2including the first margin ΔL1 to ensure receipt of the external lightincident on the channel even when the misalignment occurs in the photosensor. It is desirable that the first margin ΔL1 is at least about 7 μmwhen a degree of the misalignment of about 7 μm occurs between the firstand second substrates 100 and 200.

The gate electrode 121 of the photo switching element 120 has a largerarea than the sensor window 211 to prevent light exiting a lower portionof a first base substrate 101 from leaking out through the sensor window211. For example, the gate electrode 121 may have a third length L3extended by a second margin ΔL2 from each marginal edge of the sensorwindow 211. In an exemplary embodiment, the second margin ΔL2 is largerthan the first margin ΔL1. For example, when the second length L2 of thesensor window 211 is at least about 18 μm, the third length L3 of thegate electrode 121 is at least about 38 μm.

FIGS. 4 through 13 are plan views illustrating the photo sensoraccording to various exemplary embodiments of the present invention. Thesame reference numerals will be used to refer to the same or likeelements as those described in FIG. 1.

FIG. 4 is a plan view illustrating the photo sensor according to anexemplary embodiment of the present invention.

Referring to FIG. 4, the photo sensor includes the first substrate 100and the second substrate 200 wherein the photo switching element 110 andthe sensor window 212 are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, and the source and drain electrodes 113 and114 formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114 (asshown in FIG. 1).

The second layer 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the base substrate 201. A sensorwindow 212 is disposed at the light blocking layer 210 corresponding tothe channel (CH) of the photo switching element 110.

The sensor window 212 has a second length L2 and a second width W2. Asshown in FIG. 4, the second width W2 of the sensor window 212 may benarrower than the first width W1 of the channel (CH).

The sensor window 212 includes the first margin ΔL1 by which the sensorwindow 212 is extended from both sides of the channel (CH) in thedirection substantially perpendicular to the longitudinal direction ofthe source and drain electrodes 113 and 114 to account for misalignmentbetween the first and second substrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has a largerarea than the sensor window 211 to prevent light exiting the lowerportion of the first base substrate 101 from leaking out through thesensor window 211.

FIG. 5 is a plan view illustrating the photo sensor according to anotherexemplary embodiment of the present invention.

Referring to FIG. 5, the photo sensor includes the first substrate 100on which the photo switching element 110 is disposed and the secondsubstrate 200 on which the sensor window is disposed.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, and the source and drain electrodes 113 and114 formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114.

The second layer 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Subsensor windows 213 a are disposed at the light blocking layer 210corresponding to the channel (CH) of the photo switching element 110.

As shown in FIG. 5, the sub sensor windows 213 a are arranged along alength of the channel (CH) at a region defined by the second length L2and the second width W2. Each of the sub sensor windows 213 a has arectangular shape with the second width W2 extending in a same directionas a longitudinal length of each of the sub sensor windows 213 a. Thesecond length L2 of the region includes the first margin ΔL1 to accountfor misalignment between the first and second substrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has a largerarea than the region where the sub sensor windows 213 a are disposed toprevent light exiting the lower portion of the first base substrate 101from leaking out through the sub sensor windows 213 a.

FIG. 6 is a plan view illustrating the photo sensor according to anotherexemplary embodiment of the present invention.

Referring to FIG. 6, the photo sensor includes the first substrate 100and the second substrate 200, wherein the photo switching element 110and the sensor window are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, and the source and drain electrodes 113 and114 formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114.

The second layer 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Afirst sub sensor window 214 a and a second sub sensor window 214 b aredisposed at the light blocking layer 210 corresponding to the channel(CH) of the photo switching element 110.

The first and second sub sensor windows 214 a and 214 b are disposed atboth end portions of the region defined by the second length L2 and thesecond width W2. The first and second sub sensor windows 214 a and 214 bare spaced apart from each other along a direction of the second widthW2. Each of the first and second sub sensor windows 214 a and 214 b hasa rectangular shape with a longitudinal direction of each of the firstand second sub sensors windows 214 a and 214 b being disposed along thesecond length L2. The second length L2 of the region includes the firstmargin ΔL1 to account for misalignment between the first and secondsubstrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has an arealarger than the region where the first and second sub sensor windows 214a and 214 b are disposed to prevent light exiting the lower portion ofthe first base substrate 101 from leaking out through the first andsecond sub sensor windows 214 a and 214 b.

FIG. 7 is a plan view illustrating the photo sensor according to anotherexemplary embodiment of the present invention.

Referring to FIG. 7, the photo sensor includes the first substrate 100and the second substrate 200, wherein the photo switching element 110and the sensor window are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedby the first metal layer, and the source and drain electrodes 113 and114 formed by the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) corresponding to the source and drain electrodes 113 and 114.

The second substrate 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Aplurality of sub sensor windows 215 a are disposed at the light blockinglayer 210 corresponding to the channel (CH) of the photo switchingelement 110. Each of the sub sensor windows 215 a extends over a portionof the source electrode 113, the channel (CH) and a portion of the drainelectrode 114.

The sub sensor windows 215 a are arranged parallel to each other along alength of the channel (CH) in a region defined by the second length L2and the second width W2. The sub sensor windows 215 a extend over awidth of the channel (CH). Each of the sub sensor windows 215 a has arectangular shape with a longitudinal length of each of the sub sensorwindows 215 a extending along a same direction as the second length L2.In other words, a longer side of the rectangular shape is extended alongthe second length L2. The second length L2 of the region includes thefirst margin ΔL1 to account for misalignment between the first andsecond substrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has a largerarea than the region where the sub sensor windows 215 a are disposed toprevent light exiting the lower portion of the first base substrate 101from leaking out through the sub sensor windows 215 a.

FIG. 8 is a plan view illustrating the photo sensor according to stillanother exemplary embodiment of the present invention.

Referring to FIG. 8, the photo sensor includes the first substrate 100and the second substrate 200, wherein the photo switching element 110and the sensor window are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, and the source and drain electrodes 113 and114 formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114.

The second layer 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Aplurality of sub sensor windows 216 a are disposed in a dot matrixpattern on the light blocking layer 210 corresponding to the channel(CH) of the photo switching element 110. Each of the sub sensor windows216 a has a rectangular shape.

As shown in FIG. 8, the sub sensor windows 216 a are uniformly arrangedin rows and columns of three sub sensor windows 216 a. The columns ofthree sub sensor windows 216 a are arranged a long a length of thechannel (CH) in a region defined by the second length L2 and the secondwidth W2. Each row of sub sensor windows 216 a is disposed parallel toeach other row of sub sensor windows 216 a. Additionally, each of thecolumns of three sub sensor windows 216 a is disposed parallel to eachother such that a longitudinal length of each of the columns of threesub sensor windows 216 a extends along a same direction as the secondlength L2. The second length L2 of the region includes the first marginΔL1 to account for misalignment between the first and second substrates100 and 200.

The gate electrode 111 of the photo switching element 110 has an arealarger than an area where the sub sensor windows 216 a are disposed sothat light exiting the lower portion of the first base substrate 101 maynot leak from the sub sensor windows 216 a.

FIG. 9 is a plan view illustrating the photo sensor according to stillanother exemplary embodiment of the present invention.

Referring to FIG. 9, the photo sensor includes the first substrate 100and the second substrate 200, wherein the photo switching element 110and the sensor window are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, and the source and drain electrodes 113 and114 formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114.

The second substrate 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Aplurality of sub sensor windows 217 a are disposed in a dot matrixpattern on the light blocking layer 210 corresponding to the channel(CH) of the photo switching element 110. Each of the sub sensor windows217 a has a rectangular shape.

As shown in FIG. 9, the sub sensor windows 217 a are arrangedsubstantially similar to the sub sensor windows 216 a of FIG. 8 exceptthat the sub sensor windows 217 a of FIG. 9 are disposed in a zigzagconfiguration on a region defined by the second length L2 and the secondwidth W2. In other words, the sub sensor windows are disposed in columnsof three sub sensor windows 217 a that are disposed substantiallyparallel to each other along the second length. However, each of thecolumns of three sub sensor windows 217 a is staggered in positionrelative to each adjacent column of three sub sensor windows 217 a toform the zig-zag configuration. The second length L2 of the regionincludes the first margin ΔL1 to account for misalignment between thefirst and second substrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has an arealarger than an area where the sub sensor windows 217 a are disposed sothat light exiting the lower portion of the first base substrate 101 maynot leak from the sub sensor windows 217 a.

FIG. 10 is a plan view illustrating the photo sensor according to stillanother exemplary embodiment of the present invention.

Referring to FIG. 10, the photo sensor includes the first substrate 100and the second substrate 200, wherein the photo switching element 110and the sensor window are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, and the source and drain electrodes 113 and114 formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114.

The second substrate 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Aplurality of sub sensor windows 218 a are disposed on the light blockinglayer 210 corresponding to the channel (CH) of the photo switchingelement 110. Each of the sub sensor windows 218 a extends over a portionof the source electrode 113, the channel (CH) and a portion of the drainelectrode 114.

As shown in FIG. 10, the sub sensor windows 218 a are arranged in aregion defined by the second length L2 and the second width W2. Each ofthe sub sensor windows 218 a has an isosceles triangle shape with aheight of the triangle being the second length L2. The sub sensorwindows 218 a are arranged in a row, alternately inverted with respectto each adjacent sub sensor window 218 a. The second length L2 of theregion includes the first margin ΔL1 to account for misalignment betweenthe first and second substrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has an arealarger than an area where the sub sensor windows 218 a are disposed sothat light exiting the lower portion of the first base substrate 101 maynot leak from the sub sensor windows 218 a.

FIG. 11 is a plan view illustrating the photo sensor according to stillanother exemplary embodiment of the present invention.

Referring to FIG. 11, the photo sensor includes the first substrate 100and the second substrate 200, wherein the photo switching element 110and the sensor window are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, and the source and drain electrodes 113 and114 formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114.

The second substrate 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Aplurality of sub sensor windows 219 a are disposed at the light blockinglayer 210 corresponding to the channel (CH) of the photo switchingelement 110. Each of the sub sensor windows 219 a extends over a portionof the source electrode 113, the channel (CH) and a portion of the drainelectrode 114.

As shown in FIG. 11, the sub sensor windows 219 a are arranged in aregion defined by the second length L2 and the second width W2. Each ofthe sub sensor windows 219 a has a right triangle shape with a height ofthe triangle being the second length L2. The sub sensor windows 219 aare arranged in a row, alternately inverted with respect to eachadjacent sub sensor window 219 a. The second length L2 of the regionincludes the first margin ΔL1 to account for misalignment between thefirst and second substrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has an arealarger than an area where the sub sensor windows 219 a are disposed sothat light exiting the lower portion of the first base substrate 101 maynot leak from the sub sensor windows 219 a.

FIG. 12 is a plan view illustrating the photo sensor according to stillanother exemplary embodiment of the present invention.

Referring to FIG. 12, the photo sensor includes the first substrate 100and the second substrate 200, wherein the photo switching element 110and the sensor window are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, and the source and drain electrode 113 and114 formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114.

The second substrate 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Aplurality of sub sensor windows 220 a are disposed in a dot matrixpattern on the light blocking layer 210 corresponding to the channel(CH) of the photo switching element 110. Each of the sub sensor windows220 a has a circular shape.

As shown in the FIG. 12, the sub sensor windows 220 a are uniformlyarranged in rows and columns of three sub sensor windows 220 a. Thecolumns of three sub sensor windows 220 a are arranged in a regiondefined by the second length L2 and the second width W2. Each row of subsensor windows 220 a is disposed parallel to each other row of subsensor windows 220 a. Additionally, each of the columns of three subsensor windows 220 a is disposed parallel to each other such that alongitudinal length of each of the columns of three sub sensor windows220 a extends along a same direction as the second length L2. The secondlength L2 of the region includes the first margin ΔL1 to account formisalignment between the first and second substrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has an arealarger than an area where the sub sensor windows 220 a are disposed sothat light exiting the lower portion of the first base substrate 101 maynot leak from the sub sensor windows 220 a.

FIG. 13 is a plan view illustrating the photo sensor according to stillanother exemplary embodiment of the present invention.

Referring to FIG. 13, the photo sensor includes the first substrate 100and the second substrate 200, wherein the photo switching element 110and the sensor window are disposed at the first and second substrates100 and 200, respectively.

The photo switching element 110 includes the gate electrode 111 formedfrom the first metal layer, the source and drain electrodes 113 and 114formed from the second metal layer. The semiconductor layer 112 isdisposed between the gate electrode 111 and the source and drainelectrodes 113 and 114. The semiconductor layer 112 includes the channel(CH) disposed between the source and drain electrodes 113 and 114.

The second substrate 200 includes the second base substrate 201 and thelight blocking layer 210 disposed at the second base substrate 201. Aplurality of sub sensor windows 221 a are disposed in a dot matrixpattern on the light blocking layer 210 corresponding to the channel(CH) of the photo switching element 110. Each of the sub sensor windows221 a has a circular shape.

The sub sensor windows 221 a are arranged substantially similar to thesub sensor windows 220 a of FIG. 12 except that the sub sensor windows221 a of FIG. 13 are disposed in a zigzag configuration in a regiondefined by the second length L2 and the second width W2. In other words,the sub sensor windows are disposed in columns of three sub sensorwindows 221 a that are disposed substantially parallel to each otheralong the second length. However, each of the columns of three subsensor windows 221 a is staggered in position relative to each adjacentcolumn of three sub sensor windows 221 a to form the zig-zagconfiguration. The second length L2 of the region includes the firstmargin ΔL1 to account for misalignment between the first and secondsubstrates 100 and 200.

The gate electrode 111 of the photo switching element 110 has an arealarger than an area where the sub sensor windows 221 a are disposed sothat light exiting the lower portion of the first base substrate 101 maynot leak from the sub sensor windows 221 a.

FIG. 14 is a partial plan view illustrating a display panel according toan exemplary embodiment of the present invention. FIG. 15 is a crosssectional view taken along line II-II′ in FIG. 14.

Referring to FIGS. 14 and 15, the display panel includes an arraysubstrate 400 and a color filter substrate 500.

The array substrate 400 includes an active area AA and a light sensingarea SA for sensing light. Data lines DL, gate lines GL, switchingelements 410 coupled to the data lines DL and gate lines GL, and pixelscoupled to the respective switching elements 410 are disposed in theactive area M. Photo switching elements 450 coupled to the data lines DLand the gate lines GL are disposed in the light sensing area SA.

The color filter substrate 500 has a color filter 520 disposed in afirst region corresponding to the active region AA and a sensor window511 disposed in a second region corresponding to the light sensing areaSA. A space for each unit pixel, which is filled with the color filter520, is defined by a light blocking layer 510.

The color filter 520 includes respective color filters for red (R),green (G) and blue (B) colors to represent corresponding colors ofincident light.

Referring still to FIGS. 14 and 15, the display panel includes the arraysubstrate 400, the color filter substrate 500 facing the array substrate400 and a liquid crystal layer 600 disposed between the array substrate400 and the color filter substrate 500.

The array substrate 400 includes a transparent substrate 401, theswitching element 410, a pixel electrode 430 for a liquid crystalcapacitor (CLC) and the photo switching element 450.

The switching element 410 includes a first gate electrode 411, a firstsemiconductor layer 412, a first source electrode 413 and a first drainelectrode 414. The first gate electrode 411 is disposed at thetransparent substrate 401 and a gate insulation layer 403 is disposed atthe first gate electrode 411. The first semiconductor layer 412 isdisposed at the gate insulation layer 403 corresponding to the firstgate electrode 411.

The first semiconductor layer 412 includes a first activation layer 412a and a first resistive contact layer 412 b disposed at the firstactivation layer 412 a. A portion of the first resistive contact layer412 b is removed between the source and drain electrodes 413 and 414 sothat a channel (CH1) through which the activation layer 412 a is exposedis formed in the first semiconductor layer 412. A passivation layer 405is disposed at the first source and drain electrodes 413 and 414.

A portion of the passivation layer 405 disposed at the first drainelectrode 414 is removed to form a contact hole 416. The pixel electrode430 for a liquid crystal capacitor (CLC) is electrically coupled to thedrain electrode 414 through the contact hole 416.

The photo switching element 450 includes a second gate electrode 451electrically connected to a supplemental gate line SGL, a secondsemiconductor layer 452, a second source electrode 453 electricallyconnected to a supplemental data line SDL and a second drain electrode454. The second gate electrode 451 is disposed at the transparentsubstrate 401 and the gate insulation layer 403 is disposed at thesecond gate electrode 451. The second semiconductor layer 452 isdisposed at the gate insulation layer 403 corresponding to the secondgate electrode 451.

The second semiconductor layer 452 includes a second activation layer452 a and a second resistive contact layer 452 b disposed at the secondactivation layer 452 a. A portion of the second resistive contact layer452 b is removed between the second source and drain electrodes 453 and454 so that a second channel (CH2) having a first length L1 is disposedat the first semiconductor layer 452. A passivation layer 405 isdisposed at the second source and drain electrodes 453 and 454.

The first and second gate electrodes 411 and 451, and the first andsecond source and drain electrodes 413, 414, 453 and 454 may be formedas a single metal layer or a multi metal layer. The single or multimetal layer may include, for example, aluminum (Al), silver (Ag), copper(Cu), molybdenum (Mo), an alloy of aluminum, silver, copper ormolybdenum, chromium (Cr), tantalum (Ta) or titanium (Ti), etc.

The color filter substrate 500 includes a transparent substrate 501, thelight blocking layer 510, the color filter 520, a protective layer 530and a common electrode layer 540.

Particularly, the light blocking layer 510 defines a space for each unitpixel corresponding to the pixel electrode 430 and a region of thesensor window 511. The sensor window 511 has a second length L2 and asecond width W2 substantially similar to a structure of FIG. 1.

Particularly, the second length L2 of the sensor window 511 correspondsto the first length L1 extending from both ends of the second channel(CH2) by the first margin ΔL1 to account for misalignment between thearray substrate 400 and color filter substrate 500. For example, whenthe first length L1 is about 4 μm and the first margin ΔL1 is 7 μm, thesecond length L2 may be greater than about 18 μm.

The third length L3 of the second gate electrode 451 of the photoswitching element 450 is longer than the second length L2 of the sensorwindow 511 so that light exiting a lower portion of the transparentsubstrate 401 may be prevented from leaking out from the sensor window511. For example, the third length L3 extends beyond both sides of thesecond length L2 by the second margin ΔL2 on each respective side of thesecond length L2. For example, when the second length L2 of the sensorwindow 511 is above about 18 μm, the third length L3 is above about 38μm.

The color filter 520 includes color filters for red, green and bluecolors. A space for each unit pixel defined by the light blocking layer510 is filled with the color filter 520.

The protective layer 530 is disposed at the light blocking layer 510 andthe color filter 520 and functions as a planarization film and aprotective film. The common electrode layer 540 is a transparentconductive layer to which an electrode of the liquid crystal capacitor(CLC) is coupled. A common voltage is applied to the common electrodelayer 540.

FIG. 16 is a schematic plan view illustrating a display device accordingto an exemplary embodiment of the present invention.

Referring to FIG. 16, a liquid crystal display device 700 includes adisplay panel having a display area DA for displaying images and firstand second peripheral areas PA1 and PA2 adjacent to the display area DA.The display area DA includes an active area AA for displaying images anda light sensing area SA for sensing an intensity of external light EL.In the active area AA, switching elements TR1 are coupled to gate linesGL1 through GLn and data lines DL1 through DLm. In the light sensingarea SA, a light sensor 730 including a light switching element TR2 foroutputting a first voltage V1 (see FIG. 17) responsive to the intensityof the external light EL and a reset unit 740 for resetting the lightsensor 730 are disposed.

A gate driver circuit 710 for outputting gate signals to the gate linesGL1 through GLn is disposed in the first peripheral area PA1. The gatedriver circuit 710 may be implemented as a shift register includingstages SRC1 through SRCn+1 that are sequentially connected to oneanother. The stages SRC through SRCn+1 of the shift register output gatesignals to corresponding gate lines GL1 through GLn. The last stageSRCn+1 is a first dummy stage for driving an n-th stage SRCn.

In addition, a first driving voltage interconnection VONL to which afirst driving voltage VON is applied and a second driving voltageinterconnection VOFFL to which a second driving voltage VOFF is appliedare formed near the gate driver circuit 710 in the first peripheral areaPA1. Further, a scan start interconnection STL for providing a startsignal ST to the first stage SRC1 is formed near the first drivingvoltage interconnection VONL in the first peripheral area PA1.

A data driver circuit 720 for outputting data signals to the data linesDL1 through DLm is disposed in the second peripheral area PA2.Additionally, a read out unit 750 is disposed in the second peripheralarea PA2 to convert the first voltage V1 from the light sensor 730 intoa second voltage V2.

FIG. 17 is a circuit diagram illustrating an operation of the photosensor in FIG. 16.

Referring to FIGS. 16 and 17, the liquid crystal display device 700includes the light sensor 730, the reset unit 740, the read out unit750, a driving controller 760 and a light generation unit 800.

The light sensor 730 includes the light switching element TR2 and afirst storage capacitor CS1. The light switching element TR2 has a drainelectrode DE2 electrically coupled to the first driving voltageinterconnection VONL to receive the first driving voltage VON, a sourceelectrode SE2 electrically coupled to the first storage capacitor CS1and a gate electrode GE2 electrically coupled to the second drivingvoltage interconnection VOFFL to receive the second driving voltageVOFF.

The first storage capacitor CS1 includes a first electrode LE1electrically coupled to the second driving voltage interconnection VOFFLand a second electrode UE1 coupled to a first read out interconnectionRL1, wherein the first and second electrodes LE1 and UE1 are opposite toeach other by interposing a gate insulation layer therebetween. Thefirst storage capacitor CS1 is charged with the first voltage V1corresponding to a light current IPH outputted from the light switchingelement TR2. The light sensor 730 further includes a drain capacitor Cdelectrically coupled between the source electrode SE2 of the lightswitching element TR2 and the second driving voltage interconnectionVOFFL.

The first read out interconnection RL1 is coupled to the first storagecapacitor CS1 and the first voltage V1 charged in the first storagecapacitor CS1 is read out through the first read out interconnectionRL1.

The read out unit 750 includes a read out switching element TR3 and asecond storage capacitor CS2. The read out switching element TR3 has agate electrode GE3 for receiving a read out signal RD, a drain electrodeDE3 electrically coupled to the first read out interconnection RL1 and asource electrode SE3 electrically coupled to the second storagecapacitor CS2. When the read out switching element TR3 is turned on inresponse to the read out signal, the first voltage V1 provided from thefirst read out interconnection RL1 is transmitted to the read outswitching element TR3 and converted into the second voltage V2.

The second storage capacitor CS2 includes a first electrode LE2 coupledto the second driving voltage interconnection VOFFL and a secondelectrode UE2 coupled to a second read out interconnection RL2, whereinthe first and second electrodes LE2 and UE2 are opposite to each otherby interposing the gate insulation layer therebetween. The secondstorage capacitor CS2 is charged with the second voltage V2 that isprovided through the read out switching element TR3.

The reset unit 740 initiates the light generation unit 800 everypredetermined period of time. The reset unit 740 includes a resetswitching element TR4 having a gate electrode GE4 for receiving thestart signal ST, a drain electrode DE4 electrically coupled to the firstread out interconnection RL1 and a source electrode SE4 coupled to thesecond driving voltage interconnection VOFFL to receive the seconddriving voltage VOFF.

The reset switching element TR4 discharges the first storage capacitorCS1 to the second driving voltage VOFF through the second drivingvoltage interconnection VOFFL in response to the reset signal ST.Therefore, the reset switching element TR4 may periodically initiate ordischarge the first storage capacitor CS1.

The driving controller 760 includes an operational amplifier(hereinafter, referred to as a comparator) 761 that is electricallycoupled to the read out unit 750. The comparator 761 compares apredefined reference voltage VREF with the second voltage V2 outputtedfrom the second read out interconnection RL2. The comparator 761 outputsa first control voltage V+ or a second control voltage V− in response toa comparison between the reference voltage VREF and the second voltageV2.

The light generation unit 800 is controlled responsive to an outputvoltage VOUT of the driving controller 760. For example, in response tothe output voltage VOUT being the first control voltage V+, the lightgeneration unit 800 prevents emission of an internal light IL.Additionally, in response to the output voltage VOUT being the secondcontrol voltage V−, the light generation unit 800 emits the internallight IL. Therefore, the internal light IL exiting from the liquidcrystal display device 700 or a level of brightness is controlledresponsive to the intensity of the external light EL to reduce powerconsumption.

As described above, according to exemplary embodiments of the presentinvention, a leakage current due to misalignment between first andsecond substrates of a photo sensor may be reduced to improvereliability of the photo sensor.

Having described exemplary embodiments of the present invention, it isto be understood that the invention defined by the appended claims isnot to be limited by particular details set forth in the abovedescription as many apparent variations thereof are possible withoutdeparting from the spirit or scope thereof as hereinafter claimed.

1. A photo sensor comprising: a switching element disposed at a firstsubstrate and defined by a control electrode, a first current electrodeand a second current electrode, wherein the switching element includes achannel disposed between the first and second current electrodes, thechannel having a first length to receive an incident external light; anda second substrate on which a light receiving unit is disposed at aposition corresponding to the channel, wherein the light receiving unithas a second length longer than the first length and shorter than athird length of the control electrode.
 2. The photo sensor of claim 1,wherein the switching element includes an amorphous silicon layer thatis used for forming the channel.
 3. The photo sensor of claim 1, whereinthe second length of the light receiving unit extends beyond both endsof the channel to account for a misalignment between the first andsecond substrates.
 4. The photo sensor of claim 3, wherein the secondlength of the light receiving unit is extended from both ends of thechannel along a direction substantially perpendicular to a longitudinaldirection of the first and second current electrodes by a first margin.5. The photo sensor of claim 4, wherein the third length of the controlelectrode is extended from both ends of the light receiving unit in thedirection substantially perpendicular to the longitudinal direction ofthe first and second current electrodes by a second margin that isgreater than the first margin.
 6. The photo sensor of claim 4, whereinthe first margin is about 7 μm when the first length of the channel isabout 4 μm.
 7. The photo sensor of claim 5, wherein the second margin isabout 10 μm when the first margin is about 7 μm.
 8. The photo sensor ofclaim 1, wherein the light receiving unit includes sub sensor windowsarranged to span a width of the channel.
 9. The photo sensor of claim 8,wherein each of the sub sensor windows has a rectangular shape having alonger side corresponding to the second length.
 10. The photo sensor ofclaim 8, wherein each of the sub sensor windows has a shape of anisosceles triangle having a height corresponding to the second length.11. The photo sensor of claim 8, wherein each of the sub windows has ashape of a right triangle having a height corresponding to the secondlength.
 12. The photo sensor of claim 1, wherein the light receivingunit includes sub sensor windows arranged substantially parallel to alength of the channel.
 13. The photo sensor of claim 12, wherein each ofthe sub sensor windows has a rectangular shape having a longer sidecorresponding to a width of the channel.
 14. The photo sensor of claim12, wherein each of the sub sensor windows has a circular shape.
 15. Thephoto sensor of claim 1, wherein the light receiving unit includes subsensor windows arranged in a dot matrix pattern.
 16. The photo sensor ofclaim 1, wherein the first and second current electrodes face each otherand each of the first and second current electrodes is formed to have ashape of teeth of a comb.
 17. A display panel comprising: an arraysubstrate having an active area on which a first switching element isdisposed and a sensing area on which a second switching element isdisposed, wherein the second switching element has a channel of a firstlength; a liquid crystal layer; and an opposing substrate combined withthe array substrate to receive the liquid crystal layer, the opposingsubstrate including a sensor window corresponding to the sensing area,wherein the sensor window has a second length longer than the firstlength and shorter than a third length of a control electrode of thesecond switching element.
 18. The display panel of claim 17, wherein thesecond length of the sensor window is extended from both ends of thechannel along a direction substantially perpendicular to a longitudinaldirection of a first current electrode and a second current electrode ofthe second switching element by a first margin.
 19. The display panel ofclaim 18, wherein the third length of the control electrode is extendedfrom both ends of the sensor window in the direction substantiallyperpendicular to the longitudinal direction of the first and secondcurrent electrodes by a second margin that is greater than the firstmargin.
 20. The display panel of claim 19, wherein the first margin isabout 7 μm when the first length of the channel is about 4 μm.
 21. Thedisplay panel of claim 20, wherein the second margin is about 10 μm whenthe first margin is about 7 μm.
 22. A display device comprising: adisplay unit including pixel electrodes disposed at a first substrateand a color filter disposed at a second substrate corresponding to thepixel electrodes to display images; a light sensing unit including aswitching element having a channel of a first length disposed at thefirst substrate and a sensor window having a second length disposed atthe second substrate to sense an amount of external light, wherein thesecond length is longer than the first length; a driving controllerconfigured to output a driving control signal responsive to the amountof external light sensed by the light sensing unit; and a lightgeneration unit configured to provide the display unit with an internallight controlled by the driving control signal.
 23. The display deviceof claim 22, wherein the second length is shorter than a third length ofa control electrode of the switching element.
 24. The display device ofclaim 22, wherein the light generation unit provides an increased amountof the internal light in response to a decrease in the amount ofexternal light sensed by the light sensing unit.